1. Field of the Invention
This invention relates to methods and devices for treating tissue using photo-sensitive substances, such as biomaterials, using a catheter.
2. Description of the State of the Art
Ischemic heart disease typically results from an imbalance between the myocardial blood flow and the metabolic demand of the myocardium. Progressive atherosclerosis with increasing occlusion of coronary arteries leads to a reduction in coronary blood flow, which creates ischemic heart tissue. “Atherosclerosis” is a type of arteriosclerosis in which cells including smooth muscle cells and macrophages, fatty substances, cholesterol, cellular waste product, calcium and fibrin build up in the inner lining of a body vessel. “Arteriosclerosis” refers to the thickening and hardening of arteries. Blood flow can be further decreased by additional events such as changes in circulation that lead to hypoperfusion, vasospasm or thrombosis.
Myocardial infarction (MI) is one form of heart disease that can result from the sudden lack of supply of oxygen and other nutrients. The lack of blood supply may be caused by a closure of the coronary artery (or any other artery feeding the heart) which nourishes a particular part of the heart muscle. The cause of this event is generally attributed to arteriosclerosis in coronary vessels.
Infarct myocardial tissue may be treated by implanting cells, such as mesenchymal stem cells, skeletal myoblasts, bone marrow mononuclear cells, etc., which will facilitate the revitalization of the infarcted heart tissue. Hereafter, these types of materials, as well as solutions containing them, will be referred to as therapeutic agents, agents, biomaterials or photo-activated substances. Delivery of therapeutic agents into the infarct tissue in a minimally-invasive way generally requires that a catheter access the internal heart chamber wall in which the infarcted area exists.
Bioscaffoldings formed of two components and applied in situ to the left heart ventricle can be used to treat post-myocardial infarction tissue damage. “Bioscaffolding”, “two-component gelation system” and “gelation system” are terms that are used interchangeably in this context, and are described more fully in U.S. Pub. No. 2008/0025943. Examples of two-component gelation systems include, but are not limited to, alginate construct systems, fibrin glues and fibrin glue-like systems, self-assembled peptides, synthetic polymer systems and combinations thereof. Each component of this two-component gelation system may be co-injected to an infarct region by a dual-lumen delivery device. Examples of dual-lumen delivery devices include, but are not limited to, dual-needle left-ventricle injection devices, dual-needle transvascular wall injection devices and the like.
Another type of therapy exists to introduce chemical compound drugs, sometimes called photosensitizers, into tissue and then excites the photosensitizer in order to enable an energy transfer from the photosensitizer to a nearby oxygen molecule. This produces an excited singlet state oxygen molecule that reacts with nearby biomolecules. This reaction can cause localized damage in target atherosclerotic tissue, for example. The therapy can also be applied in oncology, and may be used to kill cancer cells after they have absorbed a pre-delivered photosensitizer. This therapy thereby provides beneficial effect to the patient.